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Open Access. Powered by Scholars. Published by Universities.®

2017

Earth Sciences

Smith College

Articles 1 - 12 of 12

Full-Text Articles in Physical Sciences and Mathematics

Pyritized Cryogenian Cyanobacteria Fossils From Arctic Alaska, Kelsey R. Moore, Tanja Bosak, Francis Macdonald, Kimberly Du, Sharon A. Newman, Daniel J.G. Lahr, Sara B. Pruss Dec 2017

Pyritized Cryogenian Cyanobacteria Fossils From Arctic Alaska, Kelsey R. Moore, Tanja Bosak, Francis Macdonald, Kimberly Du, Sharon A. Newman, Daniel J.G. Lahr, Sara B. Pruss

Geosciences: Faculty Publications

The Cryogenian was a time of climatic extremes, with two extended and severe global glaciations bracketing hothouse conditions. The effect of these extreme climate conditions on ocean chemistry and the marine biosphere remain poorly understood. Most of the previous studies of the fossil record from this interval focus on benthic organisms, with few examples of organisms with an inferred planktonic lifestyle and no firm evidence for photosynthetic organisms. Here, we present helically coiled, straight, and curved fossils composed of fine crystalline or framboidal pyrite in limestone samples from the Ikiakpuk formation of Arctic Alaska. These structures are morphologically identical to …

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Influence Of The Megathrust Earthquake Cycle On Upper-Plate Deformation In The Cascadia Forearc Of Washington State, Usa, Jaime E. Delano, Colin B. Amos, John P. Loveless, Tammy M. Rittenour, Brian L. Sherrod, Emerson M. Lynch Nov 2017

Influence Of The Megathrust Earthquake Cycle On Upper-Plate Deformation In The Cascadia Forearc Of Washington State, Usa, Jaime E. Delano, Colin B. Amos, John P. Loveless, Tammy M. Rittenour, Brian L. Sherrod, Emerson M. Lynch

Geosciences: Faculty Publications

The influence of subduction zone earthquake cycle processes on permanent forearc deformation is poorly understood. In the Cascadia subduction zone forearc of Washington State, USA, deformed and incised fluvial terraces serve as archives of longer-term (103–104 yr) strain manifest as both fluvial incision and slip on upper-plate faults. We focus on comparing these geomorphic records in the Wynoochee River valley in the southern Olympic Mountains with short-term (101 yr) deformation driven by interseismic subduction zone coupling. We use optically stimulated luminescence dating and high-resolution elevation data to characterize strath terrace incision and differential uplift across the Canyon River fault, which …

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Trilobite Extinctions, Facies Changes And The Roece Carbon Isotope Excursion At The Cambrian Series 2–3 Boundary, Great Basin, Western Usa, Luke E. Faggetter, Paul B. Wignall, Sara B. Pruss, Robert J. Newton, Yadong Sun, Stephen F. Crowley Jul 2017

Trilobite Extinctions, Facies Changes And The Roece Carbon Isotope Excursion At The Cambrian Series 2–3 Boundary, Great Basin, Western Usa, Luke E. Faggetter, Paul B. Wignall, Sara B. Pruss, Robert J. Newton, Yadong Sun, Stephen F. Crowley

Geosciences: Faculty Publications

The mass extinction of the olenellid trilobites occurred around the Cambrian Series 2–Series 3 boundary. Like many other crises, it coincided with a negative carbon isotope excursion but the associated palaeoenvironmental changes remain unclear. To investigate the causal mechanism for this event, we report facies changes, pyrite framboid petrography and carbon isotope values from Cambrian Series 2–Series 3 (traditionally Early–Middle Cambrian) boundary strata of the Carrara Formation (Death Valley region, California) and Pioche Formation (Nevada). These data reveal regionally changing water depths from high-energy, nearshore facies (oolitic grainstone) to more offshore silty marl and finer-grained carbonate mudstone. In the Carrara …

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Block Motion Changes In Japan Triggered By The 2011 Great Tohoku Earthquake, Brendan Meade, John P. Loveless Jul 2017

Block Motion Changes In Japan Triggered By The 2011 Great Tohoku Earthquake, Brendan Meade, John P. Loveless

Geosciences: Faculty Publications

Plate motions are governed by equilibrium between basal and edge forces. Great earthquakes may induce differential static stress changes across tectonic plates, enabling a new equilibrium state. Here we consider the torque balance for idealized circular plates and find a simple scalar relationship for changes in relative plate speed as a function of its size, upper mantle viscosity, and coseismic stress changes. Applied to Japan, the 2011 MW59:0 Tohoku earthquake generated coseismic stresses of 102 –105 Pa that could have induced changes in motion of small (radius 100 km) crustal blocks within Honshu. Analysis of timedependent GPS velocities, with corrections …

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The Cenomanian–Turonian Boundary In The Northwestern Part Of The Adriatic Carbonate Platform (Ćićarija Mtn., Istria, Croatia): Characteristics And Implications, Vlatko Brčić, Bosiljka Glumac, Ladislav Fuček, Anita Grizelj, Marija Horvat, Hrvoje Posilović, Ivan Mišur Jul 2017

The Cenomanian–Turonian Boundary In The Northwestern Part Of The Adriatic Carbonate Platform (Ćićarija Mtn., Istria, Croatia): Characteristics And Implications, Vlatko Brčić, Bosiljka Glumac, Ladislav Fuček, Anita Grizelj, Marija Horvat, Hrvoje Posilović, Ivan Mišur

Geosciences: Faculty Publications

The Cenomanian–Turonian boundary (CTB) in the Ćićarija Mountain region (northern Istria, Croatia) is characterized by calcisphere limestone successions with a firmground and glauconite horizon, bioturbated intervals, tempestites, and slumped structures as well as microbially laminated and organic-rich interbeds deposited in the northwestern part of the intra-Tethyan Adriatic Carbonate Platform (AdCP). Compilation of the results from three studied sections (Vodice–Jelovica, Martinjak and Planik) of litho-, bio-, and microfacies analyses, X-ray diffraction, SEM, EDS, and stable isotope analyses allowed reconstruction of marine paleoenvironmental conditions during this time period. Shallow-marine carbonate deposits of the Milna Formation underlie a drowned-platform succession of the Sveti …

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Age And Intraspecific Diversity Of Resilient Acropora Communities In Belize, Adele Irwin, Lisa Greer, Robert Humston, Meghann Devlin-Durante, Paul Cabe, Halard Lescinsky, Karl Wirth, H. Allen Curran, Iliana B. Baums Jun 2017

Age And Intraspecific Diversity Of Resilient Acropora Communities In Belize, Adele Irwin, Lisa Greer, Robert Humston, Meghann Devlin-Durante, Paul Cabe, Halard Lescinsky, Karl Wirth, H. Allen Curran, Iliana B. Baums

Geosciences: Faculty Publications

The corals Acropora palmata and A. cervicornis are important Caribbean reef-builders that have faced significant mortality in recent decades. While many studies have focused on the recent demise of these species, data from areas where Acropora spp. have continued to thrive are limited. Understanding the genetic diversity, recruitment, and temporal continuity of healthy populations of these threatened Acropora spp. and the hybrid they form (“Acropora prolifera”) may provide insights into the demographic processes governing them. We studied three reef sites with abundant A. cervicornis, A. palmata, and hybrid Acropora populations offshore of Ambergris Caye, Belize at …

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A Program Aimed Toward Inclusive Excellence For Underrepresented Undergraduate Women In The Sciences, Laura A. Katz, Kathryn M. Aloisio, Nicholas J. Horton, Minh Ly, Sara B. Pruss, Kate Queeney, Cate Rowen, Patricia Marten Dibartolo Apr 2017

A Program Aimed Toward Inclusive Excellence For Underrepresented Undergraduate Women In The Sciences, Laura A. Katz, Kathryn M. Aloisio, Nicholas J. Horton, Minh Ly, Sara B. Pruss, Kate Queeney, Cate Rowen, Patricia Marten Dibartolo

Biological Sciences: Faculty Publications

Created to foster inclusive excellence, Smith College’s Achieving Excellence in Mathematics, Engineering, and Science (AEMES) Scholars program provides early faculty-mentored research opportunities and other programming as a way to foster success in academic outcomes for underrepresented women in science. Using academic record data, we compared Scholars’ outcomes over time with those of underrepresented students before program launch and to relevant peer comparison groups. Since its launch, AEMES Scholars have achieved significantly higher gateway life sciences course grade point averages (GPAs), rates of persistence in life and natural sciences, and participation in natural sciences advanced research relative to baseline. Gains for …

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Mechanical Models Favor A Ramp Geometry For The Ventura-Pitas Point Fault, California, Scott T. Marshall, Gareth J. Funning, Hannah E. Kreuger, Susan E. Owen, John P. Loveless Feb 2017

Mechanical Models Favor A Ramp Geometry For The Ventura-Pitas Point Fault, California, Scott T. Marshall, Gareth J. Funning, Hannah E. Kreuger, Susan E. Owen, John P. Loveless

Geosciences: Faculty Publications

Recent investigations have provided new and significantly revised constraints on the subsurface structure of the Ventura-Pitas Point fault system in southern California; however, few data directly constrain fault surfaces below ~6 km depth. Here, we use geometrically complex three-dimensional mechanical models driven by current geodetic strain rates to test two proposed subsurface models of the fault system. We find that the model that incorporates a ramp geometry for the Ventura-Pitas Point fault better reproduces both the regional long term geologic slip rate data and interseismic GPS observations of uplift in the Santa Ynez Mountains. The model-calculated average reverse slip rate …

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Super-Interseismic Periods: Redefining Earthquake Recurrence, John P. Loveless Feb 2017

Super-Interseismic Periods: Redefining Earthquake Recurrence, John P. Loveless

Geosciences: Faculty Publications

Precise geodetic measurements made over broad swaths of tectonically active regions record patterns of interseismic strain accumulation, providing key insights into the locus and timing of pending earthquakes. Recent studies of geodetic position time series, including that of Melnick et al. (2017), illustrate temporal variation in the pattern of interseismic deformation. These authors propose that the 2010 Mw = 8.8 Maule, Chile, earthquake enhanced coupling on the Andean subduction zone adjacent to the rupture, including on the portion of the megathrust that broke 5 years later in the Mw = 8.3 Illapel event.

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Callianassid Shrimp Diversity Around San Salvador Island, Bahamas: Why Marine Biologists And Geologists Should Care, H. Allen Curran, Koji Seike Jan 2017

Callianassid Shrimp Diversity Around San Salvador Island, Bahamas: Why Marine Biologists And Geologists Should Care, H. Allen Curran, Koji Seike

Geosciences: Faculty Publications

Reprinted from: Carol L. Landry, Lee J. Florea, & Daniel S. Kjar (eds.), Proceedings of the 1st Joint Symposium on the Natural History and Geology of The Bahamas: San Salvador, Gerace Research Centre

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Imaging Bioturbation In Supratidal Carbonates: Non-Invasive Field Techniques Enhance Neoichnological And Zoogeomorphological Research, San Salvador, The Bahamas, Karen Kopcznski, Ilya Buynevich, H. Allen Curran, Jon Caris, Jonathan Nyquist Jan 2017

Imaging Bioturbation In Supratidal Carbonates: Non-Invasive Field Techniques Enhance Neoichnological And Zoogeomorphological Research, San Salvador, The Bahamas, Karen Kopcznski, Ilya Buynevich, H. Allen Curran, Jon Caris, Jonathan Nyquist

Geosciences: Faculty Publications

A case study in unconsolidated carbonates on San Salvador Island, The Bahamas, utilized high-frequency (800 MHz) georadar imaging to augment existing methodologies (burrow counts and measurements, casting) in brachyuran bioturbation research (Ocypode quadrata and Gecarcinus lateralis), and as part of a new dataset characterizing blue land crab (Cardisoma guanhumi) burrows. Non-invasive techniques such as ground-penetrating radar (GPR) can complement traditional field surveys aimed at quantifying mesoscale bioturbation in modern settings. These methods can establish diagnostic features for tracemaker identification and refine existing ichnofacies models. Drone-mounted aerial coverage provided the first high-resolution images of the micro-topography and …

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Post-Rift Magmatic Evolution Of The Eastern North American “Passive-Aggressive” Margin, Sarah E. Mazza, Esteban Gazel, Elizabeth A. Johnson, Michael Bizimis, Ryan Mcaleer, C. Berk Biryol Jan 2017

Post-Rift Magmatic Evolution Of The Eastern North American “Passive-Aggressive” Margin, Sarah E. Mazza, Esteban Gazel, Elizabeth A. Johnson, Michael Bizimis, Ryan Mcaleer, C. Berk Biryol

Geosciences: Faculty Publications

Understanding the evolution of passive margins requires knowledge of temporal and chemical constraints on magmatism following the transition from supercontinent to rifting, to post-rifting evolution. The Eastern North American Margin (ENAM) is an ideal study location as several magmatic pulses occurred in the 200 My following rifting. In particular, the Virginia-West Virginia region of the ENAM has experienced two postrift magmatic pulses at ∼152 Ma and 47 Ma, and thus provides a unique opportunity to study the long-term magmatic evolution of passive margins. Here we present a comprehensive set of geochemical data that includes new Ar/ Ar ages, major and …

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